21.

Membrane-bound and free ribosomes, are structurally identical, but differ only at a given time in terms of association with

• acetylated proteins

• glycosylated proteins

• phospholipids

• nascent proteins

The dye used in Gram staining is

• Rhodamine

• Methylene blue

• Giemsa

• Crystal violet

Each origin of replication is activated only once. This is achieved because

• pre-replicative complex can only form in G1 and replication can only be initiated when the pre-replication complex is disassembled at the beginning of S-phase.

• replication can only be initiated when pre-replication complex is intact.

• replication can only be initiated when unphosphorylated Rb is present.

• pre-replicative complex can only form S-phase.

Electron microscopes have much higher resolution than any type of light microscope because

• of their higher maginification.

• the lenses used are of much higher quality

• of very short wave length of electrons.

• the images are viewed on screen rather than directly using an eye-piece or occular lens.

Histone acetylase and chromatin remodeling complexes are recruited to specific regions of chromatin by

• gene activator proteins.

• specific promoter sequence

• phosphorylation of histone acetylase

• dephosphorylation of chromatin remodeling complexes

Which one of the following statements is NOT correct for propagation and maintenance of mammalian cells in vitro?

• Transformed cell lines do need external supply of serum to grow.

• The cells that are obtained directly from the organism is a primary culture.

• Trypsin is added to cell culture media to maintain cell's death.

• HEPES buffer is generally used to maintain pH of the culture media.

A bioinformatics tool used to find the sequence similarity in the subunits of hemoglobin is

• FASTA

• BLAST

• HUMMER

• PSI:PLOT

The electrospray ionization spectrum of a highly purified protein shows multiple closely spaced peaks. This most likely arises due to

• degradation of the protein during recording of the spectrum.

• the presence of multiple conformations.

• multiple charged species of the protein.

• extensive aggregation of the protein.

The average energy absorbed by 10 gm of tissue from ³²P radiation is 14.9 Jkg^-1. The average dose in rads is

• 1490

• 1.49

• 14900

• 149

In isoelectric focusing experiments, proteins are separated on the basis of their

• relative content of only positively charged residues.

• relative content of only charged residues.

• relative content of positively and negatively charged residues.

• mass to charge ratios